Bombus neoboreus Sladen

Williams, Paul H., Berezin, Mikhail V., Cannings, Sydney G., Cederberg, Björn, Ødegaard, Frode, Rasmussen, Claus, Richardson, Leif L., Rykken, Jessica, Sheffield, Cory S., Thanoosing, Chawatat & Byvaltsev, Alexandr M., 2019, The arctic and alpine bumblebees of the subgenus Alpinobombus revised from integrative assessment of species’ gene coalescents and morphology (Hymenoptera, Apidae, Bombus), Zootaxa 4625 (1), pp. 1-68 : 37-39

6. Bombus neoboreus Sladen

( Figs. 89‒103 , 134 , 143 , 145 , 148 )

B.<ombus> strenuus Cresson 1863:102 (not of Harris 1776:131, = B. lapidarius (Linnaeus)) , type-locality citation ‘Youcon River, Arctic America, and Hudson’s Bay Territory’. Lectotype queen (#4706) by designation of Cresson 1916:131, ANSP examined PW, ‘H. B. T.’ [Hudson Bay Territory] (? Nunavut, Canada).

Bombus neoboreus Sladen 1919:28 , type-locality citation ‘Bernard harbour, Northwest Territories’. Lectotype queen (#4406) by designation of Milliron 1973:110, CNC examined PW, ‘Bernard / Harbour’ (formerly NWT, now Nunavut, Canada). Synonymised with Megabombus strenuus (Cresson) by Milliron 1973:108).

[ Bombus neoboreus (strenuous) Cresson; Kearns & Thomson 2001:97, incorrect subsequent spelling.]

Taxonomy and variation. Bombus neoboreus has long been treated as including B. kluanensis but has been recognized as separate from evidence of a species coalescent in the COI gene ( Williams et al. 2015; Fig. 9 ), differences in morphology and differences in the PEPCK gene (Williams, Cannings, et al. 2016).

Variation in the colour pattern has been illustrated and analysed previously ( Williams et al. 2014; Williams et al. 2015).

The pale colour pattern B. strenuus Cresson was described as having the hair of the dorsal part of the side of the thorax, the scutellum, and T1‒3 extensively yellow ( Figs. 90‒93, 101‒102 ). This is the most widespread colour pattern of the species. The principal variation is in whether T5 is predominantly orange ( Figs. 90, 92‒93, 101‒102 ) or predominantly black ( Fig. 91 ), although there are usually a few orange hairs present.

Later, the darker colour pattern B. neoboreus was described, which has the dorsal part of the side of the thorax, the scutellum, and T3 extensively black ( Figs. 94‒100, 103 ). The darkest females have the top of the head, side of the thorax, scutellum, middle third of T1, and T3‒5 black ( Fig. 97 ). There are especially many individuals of the dark colour pattern neoboreus s. str. in collections from Nunavut: near Coppermine, Bernard Harbour, and Kugluktuk. They are superficially similar to some B. polaris , but are slightly larger, with shorter hair, have a longer oculomalar distance, and have a smoother shinier outer corbicular surface of the hind tibia. Individuals with both colour patterns (the pale strenuus and the dark neoboreus s. str.) co-occur at Kluane (Yukon) and at Coppermine (Nunavut) and there are no diagnostic differences in their COI barcodes.

Material examined. 58 queens 104 workers 100 males (plus 5 females with caste undetermined), from the USA and Canada ( Fig. 89 : AMNH ANSP CNC INHS NHMUK NMNH PCYU PR PW RBCM RSKM RSM UAM YPM), with 15 specimens barcoded. A record of a queen from a site on Vancouver Island (#4298) was noted by Milliron (1973) as needing confirmation. The specimen ( CNC) is correctly identified, but the site is unexpectedly far south for this species and at low elevation, apparently in unusual forest habitat for this species (cf. the Maxent climatic suitability model in Fig. 7 ), so the specimen may have been mislabelled.

Habitat and distribution. Flower-rich arctic/alpine tundra in the New World tundra excluding Greenland, north to Prince Patrick Island and east to Victoria Island, extending southwards into the subarctic region in the alpine zone of the Alaskan and Yukon mountains. Regional distribution maps ( Milliron 1973; Williams et al. 2014).

Food plants. Unknown.

Behaviour. Unknown.

Conservation status. This species has not yet been fully assessed for Red List threat status using IUCN criteria (2001). Hatfield et al. (2016c) have listed B. neoboreus as ‘Data deficient’. Their data appear to include data for B. kluanensis .

Figures

FIGURE 7. Sample sites and climatic suitability for all Alpinobombus species combined estimated using Maxent from climate variables for the year 2000. Bright yellow and brown areas show where the logistic prediction of occurrence is p> 0.5 (the outlier records with exceptionally low probabilities of suitability were excluded in step-wise iterations); brown spots show all consistent Alpinobombus site records; ‘?’ shows the five records that are in climatically outlying sites. Polar projection, North Pole (starred) at the centre of the map, international boundaries and the Arctic Circle shown as narrow grey lines.

FIGURE 9. Estimate of the metric gene tree for the 54 longest unique COI-barcode alleles of the subgenus Alpinobombus from MrBayes combined with the Bayesian Poisson-tree-process (PTP) solution with the highest support with spots showing the nodes with the strongest support as coalescents for candidate species (outgroup B. ignitus not shown). Values above the nodes are Bayesian posterior probabilities showing branch support for groups; values below the nodes are PTP Bayesian support values that all daughter alleles are parts of a single species (probabilities within candidate species are all ≤ 0.44). The scale bar is calibrated in substitutions per nucleotide site. Each unique allele is represented by one of the longest available sample sequences, labelled with: the sequence length in number of nucleotides, a taxon name or name describing an unpublished colour pattern, and then a code that consists of a specimen identifier (AL#n) from the project database and (after the hyphen) a sample identifier from BOLD or GenBank, followed with its geographic origin (for simplicity Greenland is included without Denmark).

FIGURES 89‒103. 89: Bombus neoboreus global distribution (as for Fig. 15). 90‒103 colour patterns (as for Figs. 16‒21): 90 (#68) USA-Alaska; 91 (#4706) Canada-Nunavut; 92 (#3816) Canada-Yukon; 93 (#3819) USA-Alaska; 94 (#2055) Canada-Nunavut; 95 (#2058) Canada-Nunavut; 96 (#2071) Canada-Nunavut; 97 (#2051) Canada-Nunavut; 98 (#4406) Canada-Nunavut; 99 (#90) Canada-Nunavut; 100 (#92) Canada-Nunavut; 101 (#93) Canada-Yukon; 102 (#3762) Canada-Nunavut; 103 (#91) Canada-Nunavut.

FIGURES 129‒137. Morphology of the male genitalia for species of the subgenus Alpinobombus from the dorsal aspect, anterior to the left of the image, posterior to the right: 129 B. alpinus (#3824); 130 B pyrrhopygus (#3833); 131 B. polaris (#73); 132 B. balteatus (#3843); 133 B. kirbiellus (#3768); 134 B. neoboreus (#4387); 135 B. kluanensis (#4876); 136 B. natvigi (#81); 137 B. hyperboreus (#3821).

FIGURES 140‒143. Morphology of females (queens). Left lateral aspect of the oculo-malar area of: 140, B. polaris; 141, B. kirbiellus (white lines indicate length and breadth measurements). Left lateral aspect of the outer surface of the left hind tibia (corbicular area): 142, B. polaris; 143, B. neoboreus (white lines indicate highlights in the central area).

FIGURES 144‒147. Morphology of males. Dorsal aspect of the penis valves of: 144, B. natvigi; 145, B. neoboreus (white lines indicate location of the subapical outer tooth of the left penis valve). Dorsal aspect of left gonostylus: 146 B. kirbiellus; 147, B. polaris (white lines indicate anterior, midpoint, and posterior median projections of left gonostylus).

FIGURES 148‒149. Anterior / left lateral aspect of the lower part of the clypeus, the labrum, and the mandibles of males of: (148) B. neoboreus (#4867), showing the small orange hair patches at the base of the mandibles and the long dense posterior fringing black beard; (149) B. kluanensis (#4876), showing the large dense orange hair pads on the mandibles and the sparse orange hairs in the posterior fringing beard.